The evolution of the eye

Model organisms are species that are studied extensively to understand particular biological phenomena and processes, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms.

The small marine ringed worm Platynereis dumerilii gained interest as a lab organism because of the dependency of its reproduction on the lunar cycle. For optimal breeding conditions in the lab, the worms experience summer all year round – they’re exposed to 16 hours of light and 8 hours of total darkness each day.

Scientists use Platynereis dumerilii to study the development of its eyes – the simplest amongst all animals, consisting of only two cells. As Platynereis dumerilii is one of the oldest species still existing, studying this ringed worm’s eyes also means studying the developmental evolution of eyes in general.